I have Windows 7 Professional SP1 v6.1.7601 x64. I have used VirtualBox 4.2.12 and all works just fine, but few days ago decide to upgrade to 4.3.0, so i uninstall current VirtualBox, reboot, download VirtualBox-4.3.0-89960-Win.exe form Oracle site, install it (with admin rights) and reboot. Then i try to start it (VirtualBox.exe) and it say:

I found tonns of posts with the same error over the internet, but none of them helps.

What i tried to do to fix that:- check all disks for errors- reinstall VirtualBox- manually delete folders like .VirtualBox from users folder- manually delete all records of VirtualBox from Windows Registry- do restore of Windows system files (sfc /scannow)- manually register VBoxC.dll

Start All ProgramsOracle VM Virtualbox Right click on the exe and click on PropertiesUnder compatibility select compatibility for windows xp service pack 3Save and run again as adminIt worked for me without issues Upgraded the extension pack and i am good to go

Problem seems to have been solved by going into properties->compatibility and checking Execute this program in compatibility mode and Execute this program as administrator, then clicking Modify parameters for all users.

The Cause of the ProblemThere was a storm that passed through my city, and when I came home, I had lost all power in my house, including power to my computer running VirtualBox and my LAMP server. This error mentions that '<' was not found in the XML file located at this directory: C:\Users\username\.VirtualBox\VirtualBox.xml. You might have to set folds to show hidden folders and files to see this directory. When looking at the VirtualBox.xml file in this directory, the size of the file was 0KB, and when opening the XML file in notepad, it was completely empty. I suspect the storm/power outage somehow resulted in this file losing all of it's data.

Steps to ResolveFirst, I uninstalled VirtualBox. Next, I removed the VirtualBox.xml file from the C:\Users\username\.VirtualBox\ directory. I then reinstalled VirtualBox, and confirmed that the XML was rewritten, and it was now 2 KB, and contained data. The error no longer appears, and I'm able to launch VirtualBox, and rebuild my LAMP (which only took 10 minutes).